Telephone companies have long used a plurality of remote terminals (RT) interconnected via high speed lines to central offices (CO) for economical distribution of “plain old telephone service” (POTS) via unshielded twisted pairs (UTP). COs are costly to build and maintain. Further, service from a CO over UTP is more difficult at increasing distances from the CO, especially distances over 20,000 feet. On the other hand, an RT can be installed on a very small amount of real estate. Also, the expenses involved in distributing and connecting the UTPs to customers from an RT is significantly less than the expenses associated with a CO at longer distances.
Although there are many types of remote terminals, controlled environment vaults (CEV), and so forth, a common limitation of those in existence for 20 years or more is that they were equipped to provide narrowband services only, and have no room for additional racks of equipment to provide broadband services. Many of today's customers want the capability of digital subscriber line (DSL) service and other advanced broadband services, electrically, optically or otherwise. DSL circuitry requires much more power than does POTS, partly because it is always in an ON condition. Thus, even if there was room in an enclosure for additional service such as DSL circuitry, the power generating system contained in a typical enclosure does not have sufficient additional capacity. The RTs also include batteries for backup power to keep telephone service operating during electrical power outages. Any increase of power usage in a RT would therefore reduce the backup time of the battery system. Thus, to maintain backup standards, additional batteries and space for the batteries would be required.
A typical small remote terminal would have room for one channel bank of POTS cards and one plug-in power system. The term “plug-in” is intended to define components with male or female connectors that can be quickly and easily replaced with new, or at least operable, components when an old component fails. A power system, as originally designed, would typically comprise one or two ring generators, a set of batteries, an alternating current (AC) rectifier and battery charger, a power and jack panel box, and a sensing circuit to switch the load between the rectifier and the batteries when the AC power is interrupted. A typical larger RT would have room for up to 4 channel banks and 2 power systems.
There has been no source of suitable replacement components of RT power systems for many years. The sensing circuit of the power system in the 1970s style RTs has been especially vulnerable to failure. A similar but different design of RT was introduced in the 1980s. The power system had slightly fewer individual components and somewhat different plug-in connectors but otherwise operated in substantially the same manner as the older RTs. Again, no new replacement power systems are available for the 1980s style RTs. It should be noted that since the interconnections were different, the power supplies of the newer systems could not be utilized in the older RT cabinets even if all the functional capabilities were identical. The non-identical functional capabilities include that at least some of the event-alarm signal conditions were configured differently from the conditions in the older RT cabinets.
It is standard practice in the telecommunications industry to fuse all wires emanating from a power system component box or enclosure, to the extent possible. The power systems in the above-referenced RTs thus had many fuses covering a major portion of the surface of the power and jack panel box that did not already contain test points and other connectors. Therefore, even if there was adequate power capability to power DSL circuits, there was no room in the old power systems for additional fuses or connections to any added circuits and required additional batteries.
It should further be noted that many of the power systems in the above-mentioned older RTs have no redundancy in the rectifier AC/DC conversion portion. Therefore, if a single component failed in the rectifier AC/DC portion, power was forced to be drawn from the batteries, alarms were raised and immediate maintenance attention was required to avert loss of telephone service to a large number of customers. Neither of the above-mentioned RTs utilized temperature compensation in the charging circuits for the batteries. For this reason, some of the maintenance calls required premature replacement of batteries, prior to the time they would have failed if environmental temperature were taken into account when determining the voltage at which the batteries were being charged, and thereby increased maintenance costs.
Another problem is that the controller for various sub-modules dictates all the sub-module actions. Thus when the controller fails, the entire system must be shutdown prior to replacement of the controller.
The power supplies used in these RTs were of a design that generated a considerable amount of heat. The RT enclosures, however, used passive heat dissipation as opposed to active means such as fans for removing heat from the enclosure. Thus the addition of any additional circuitry to an RT enclosure, while using a power source of the original design, would require attention to the heat dissipation of that circuitry.
Therefore, there is a need for a replacement power system that is plug-compatible with present power systems that are failing. Further, there is a need for power systems that can supply adequate power to an RT utilizing broadband circuitry and optics, as well as connect to and charge additional batteries, and/or provide additional over-current protected load connections. Even further, there is a need to reduce the size of any replacement power system, so that space is made available for additional banks of advanced broadband circuitry and optics that would otherwise have to be deployed in one or more additional or adjunct RT enclosures. Also, there is a need for redundancy in rectifying circuitry whereby the failure of a single component of the rectifying circuitry does not necessarily prevent the generation of power to a load. Additionally, there is a need to be able to replace the controller without shutting down the entire system in the RT and thus preventing calls by a large number of connected customers. Still further, there is a need to reduce maintenance costs by controlling the battery charging voltage as a function of temperature. Finally, there is a need to reduce the heat generated by any replacement power source to accommodate heat dissipated by any additional advanced broadband circuitry within the enclosure.